The present invention relates to an arrangement for detecting rollover events in vehicles.
If a rollover of a vehicle occurs, all the occupant protection mechanisms installed in the vehicle must be activated in timely fashion. Such occupant protection mechanisms include, for example, rollover bars, belt tensioners front and side airbags, fold-down seat locks in a commercial vehicle, etc. In order for all these protection mechanisms to be activated in timely fashion, it is necessary to detect, as early as possible, whether rotations of the vehicle about its vertical axis (yaw axis), longitudinal axis (roll axis), and transverse axis (pitch axis) will lead to a rollover. To ensure also that the occupant protection mechanisms are in fact activated only in the event of a rollover, incorrect detections of rollovers should be excluded to the greatest extent possible.
German Patent No. 36 04 216 C2 describes a rollover sensor consisting of a fluid-filled space in which a body, suspended in the manner of a pendulum, is located as a seismic mass. By means of an electrical analysis circuit, changes in the position of the pendulum, which can deflect in any direction, yield a datum as to whether or not the vehicle is rolling over. This rollover sensor based on the pendulum principle has the disadvantage on the one hand that it reacts too slowly to vehicle movements, so that a rollover might possibly be signaled too late to activate the occupant protection mechanisms, and on the other hand that a rollover event can be imitated by resonant vibrations of the seismic mass.
European Patent No. 0 430 813 B1 describes a system for vehicle rollover detection which has one rotation rate sensor and three acceleration sensors. The rotation rate sensor measures the angular velocity about the roll axis of the vehicle, and the three acceleration sensors measure the acceleration of the vehicle in the direction of its longitudinal axis, transverse axis, and vertical axis. From the measured angular velocity and the measured accelerations, three variables are derived which are each subjected to a threshold decision. As soon as one of the three variables exceeds the threshold defined for it, a decision is made that a vehicle rollover is about to occur.